United Flight 1219 departed Denver at 11:40 a.m. Sunday. It was scheduled to be a direct flight to Hawaii.

Rich and Kristin Anderson were heading to Kauai to celebrate their wedding anniversary, but when they were halfway over the Pacific Ocean, there was a disturbing announcement.

“We were probably three hours from Hawaii and they announced that the toilets were all full,” Kristin Anderson said.

The pilot told passengers the toilets had not been serviced in Denver. “The pilots failed. They didn’t do their job. This should not have happened. This was human error. There was no act of God. There was no weather. This was just human error.”

They were forced to double back and land in San Francisco to fix the problem. The situation meant the scheduled flight time went from eight hours to more than 16 hours.

“The pilots failed. They didn’t do their job. This should not have happened. This was human error. There was no act of God. There was no weather. This was just human error,” Rich Anderson said.

Earlier in the flight, Anderson tried to use one of the bathrooms but it was locked.

“They had locked them. I had gone back partway through to the bathroom and one of them was locked. The flight attendant said that one is not working. I think they were locking them as they were filling up," Anderson said.

“I am very sorry that our lavatories had reached capacity while Flight 1219 was en route to Lihue," the airline said in a letter to passengers. "A decision was made to turn back and land in San Francisco where arrangements were made to change planes. I can appreciate that this experience was disappointing and unpleasant."

"We regret the unexpected delay and inconvenience this caused you. Your satisfaction is important to us so I hope you will accept our offer of apology on the next screen."

"We welcome the opportunity to provide better service for you the next time you fly with United.”

United is offering 10,000 bonus miles or a $200 travel voucher to affected passengers. But the Andersons said that is not fair compensation, given everything they went through.

“Bottom line is they ruined a lot of people’s vacations yesterday. They gave us a really crummy start. There were a lot of elderly people and people with little tiny kids,” Rich Anderson said.

It's not known why the lavatories were not properly serviced in Denver before the flight was cleared for takeoff.